The use of robotic welding machines is prevalent throughout many industries today. Robotic welders are versatile, efficient, and when operating properly they consistently produce high quality welds, making them an important element of many manufacturing processes. While robotic welding machines generally can be found in a variety of configurations, they universally suffer problems from shunt cables (power supply cables) that fail unexpectedly during service. Shunt cables typically fail as a result of mechanical flexing caused by robotic motion of the welding machine. The flexing causes cable strands to fatigue and eventually leads to increased cable resistance and breakage.
As a cable begins to fatigue, the electrical resistance of the cable increases. The higher cable resistance causes a reduction in current flow through the cable to the welding tips. This in turn causes the welding machine to produce "cold welds" which are highly susceptible to failure. A typical manufacturing plant may have dozens of robotic welding machines and significant production losses can occur while maintenance technicians attempt to locate and repair a problem cable.
It is estimated that 90% of unscheduled robotic welder downtown is attributable to shunt cable failures. Therefore, elimination of this downtime causal factor would represent a quantum leap in reducing the costs and production losses associated with unscheduled downtime. Unfortunately, there are currently no known procedures for effectively and efficiently determining when a shunt cable is fatigued and near breakage. Resistance meters and thermographic scanners are readily available for this task, but neither offers the ability to measure cable resistance continuously and automatically alert plant personnel of an impending cable failure. Although manufacturers are working to develop cables that last longer, extending cable life has proven difficult due to the high electrical currents that these cables carry and the continuous flexing they endure during welding operations.
Therefore, there is a need for a continuous, on-line, welder cable monitor capable of predicting and isolating shunt cable failures so that fatigued cables can be efficiently repaired with a minimum of production downtime.